1. Technical Field of the Invention
The present invention relates to an improvement of a cooling apparatus of a false texturing machine, such as a draw texturing machine or a false twist texturing machine. More specifically, the present invention relates to a cooling apparatus of a false texturing machine, by which so called surging phenomenon can be prevented from occurring during the high speed false twisting operation. The so called surging phenomenon refers to a phenomenon wherein a yarn undergoes ballooning, i.e., a kind of rolling of a yarn in a twisting zone when the false twist texturing speed is excessively increased, with abnormal variation in tension of the twisted yarn resulting.
2. Description of Prior Art
A known false texturing machine comprises a false twisting device for imparting twists to a yarn, and a heating apparatus, disposed upstream from the false twisting device, for heat setting twists that run back along the yarn. Further, a known draw texturing machine is provided with a drawing device for drawing the yarn at a predetermined draw ratio prior to or simultaneously with the twist setting by the above-described heating apparatus and the false twisting device.
In a conventional operation, wherein false twist texturing speed is up to 100 m/min, it is sufficient for a yarn to be cooled naturally just after it is heat set by the heating apparatus. In other words, no specifically designed cooling apparatus is required.
However, as the false twist texturing speed increases, the yarn cannot be fully cooled only by conventional natural cooling. In addition, when the twisted yarn runs at a high speed, ballooning at the cooling region increases. Thus, a yarn is forced to run in contact with a cooling apparatus so as to restrict occurrence of the ballooning.
When the false twist texturing speed is further increased and reaches a super high speed, i.e., a speed equal to or higher than 1,000 m/min, a surging phenomenon, i.e., a large waved vibration, occurs in a yarn running through the cooling apparatus. More specifically, the yarn is subjected to ballooning, i.e., rolling, in the twisting zone, and abnormal variation in tension of the twisted yarn occurs. Especially when a high temperature heating apparatus, wherein a yarn is heated to a temperature higher than 300.degree. C., is used, unevenness in dyeing or yarn breakages may occur easily.
It is possible to increase the tension in yarn at the false twisting region in order to obviate the surging phenomenon. However, if this measure is adapted, crimp characteristic in the obtained textured yarn may be adversely affected and yarn breakages may be increased. Consequently, the above-described measure, wherein tension in the yarn at the false twisting zone is enhanced, has a limit for preventing the surging phenomenon.
As another measure for preventing the surging phenomenon, it is possible to shorten the length of a cooling apparatus and to cool the cooling apparatus by means of water or another cooling medium. More specifically, the length of the cooling apparatus is shortened to about 500 mm, and two short cooling apparatus are prepared, and the yarn contacting surfaces of such cooling apparatus are forcibly cooled by means of a cooling medium such as water. However, the construction of the cooling apparatus may be complicated if this measure is applied, and accordingly, the equipment cost and correspondingly the cost for manufacturing false textured yarns are increased.